Electric alarm systems



May 5, 1964 M. DONNER ELECTRIC ALARM SYSTEMS Filed April 30, 1962 REC. l

LOUDSPEAKER- VOLTAGE LIMITING 0 1: V 2/ MEANS VOLTAGE LIMITING MEANSVOLTAGE LIMITING MEANS VOLTAGE LI M I Tl NG MEANS INVENTOR MEIER DONNERtrol station, to .modulators in order to produce currents modulated bythe signals.

' My copending US. application Sen-No. 117,002, of

June14, 1961, under the title Electric alarm system,

describes a system adapted to detect unauthorized passagesatpredetermined points, thedetecting means being constituted byseismographs positioned under ground.

Said prior application describes also a system for processing theelectric voltages collected by the seismographs,

'said Voltages acting, whenever they rise above a prede terminedthreshold, on electronic; multivibrators which act in'their turn on anysuitablealarm system. Said prior application further describes variousmodifications which increase the sensitivity of such multivibrators,under the 7 action of signals having a steep front.

' My present invention more particularly is. directed to improvements inthe indicating members incorporated with. detecting systems of the typereferred to, said indi- United States Patent eating members being fed bythe voltages across the teraninals of the seismographs.v

It covers more particularly embodiments constituted by a complete systemadapted to investigate a large area carrying a large number of groups ofseisrnog-raphs, which seismog'raphs feed information to a controlstation, which allows asmall number of operators at said station toinvestigate the whole'area to' be considered.

My invention has chiefly for its object to further such an investigationtogether with the discrimination to be obtained between the usefulsignals and parasitic noises, while it. reduces the probability ofanuntimely alarm and improves thus, generally speaking, the efficiency ofthe j investigation.

According to my invention'and in order to further the investigationoperations andto draw immediately the attention of the operators whenthe seismographsdetect signals of interest, the voltages supplied by thedifferent 'seismographs areapplied to a single loud-speaker However, theinsertion in series or in pa fl lel of the voltages fed bytheseismographs with a view. to feeding therewith a single loud-speaker,cannot provide usable results, since this would only show thesum of thevoltages .(or intensities) corresponding to said signals, which latterwould lose their individuality and the indications given out bythe'loud-speaker would befmeaningless, as may easily be proved byexperience. p

To this end, and in accordance with a first feature of my presentinvention, and with a view to retaining the individualization of thesignals, the voltages collected by the different groups of seismographs,are fed at the concarrier Experience shows that the useful signalsserving for the detection of any tentative passage over apredeterminedarea, are constituted by signals of avery low frequency,said frequency being lower than about l00 cycles.- 4, Consequently, achannel adapted to transmitthe signals collected by a group ofseismographs, may, without any -drawback, be given a band width limitedto about 200 cycles (0 to 200 cycles) and the frequency of the carrierwave used may therefore be selected within the range of audiblefiequencies. I

:It is immediately apparent that it is easily possible to obtain withinthe range of audible frequencies, to wit: 500 to 10,000 cycles, abouttransmission channels 3,132,330 Patented May 5, 1 964 Ice ferentchannels.

According to my invention, the voltages provided by these differentchannels are merely added and applied to a single loud-speaker. Y Theinterest of said last feature resides in the fact proved by experiencethat the human ear readily" detects, among a system of sounds, thecharacteristic features of those sounds which occupy apredetermined bandof fre: quencies. v v

Said property of the human ear allows it to select among all the signalsreprodilced in bulk by the loudspeaker, that signal or those signals ofa predetermined channel. Said feature of my invention allows an acousticinvestigation by a single operator of the whole alarm system, whichwould be obviously impossible, if it were necessary toprovide as manyloud-speakers as; there are groups of seismographs.

This novel feature provides furthermore, a substantial simplification inthe equipment of the control station, since it allows reducing to asingle loud-sneaker the whole system of acoustic alarm means at'saidstation.

According to a still further feature of my invention, the controlstation may also be provided with. optical alarm means constituted forinstance, by indicators or by illuminated tubes of the magic eye type,or else by luminous points. J i

In the case of the use of illuminated tubes of the magic eye type, theoptical indication supplied is provided by.a luminous surface the shapeof which defines the voltage applied to the. indicator. V

'In-the case ,where a luminuous source such as an incandescent bulb isused, the luminous intensity of the source maybe controlled so as todefine a function of thesignal voltage applied to the indicator or else,according-to a still further feature of my invention, it is possible toresort to a source of intermittent light having a constant or variableluminosity and the frequency of illumination of which depends on theamplitude of the signals applied to it.

. The voltages fed by the seismog raphs may vary within a very largerange; In contradistinctiou, the range of variations ofthevoltagesapplicable to the luminous indications between a minim umvoltage providing a useful indication and the maximum voltage whichrnaybe ap plied, is much more restricted and consequently I'preferresorting, according to my invention, for each. group, of seismographs,toa system of optical indicators of decreasingsensitivity, saidindicators being fed through intensity limiting means withinput'voltages the values of which increase preferably in accordancewith a geometrical progression; a v H Further features and advantages ofmy invention will appear, in the readingof the following description,refer,- ence beingmade to thesingle figure. of the accompanying drawingswhich illustrates the circuits relating to a predetermined channel witha singleldud-speaker and theassociated optic indicators.

' As illustrated, a group of seisrriographsl i siadapted to providevoltages to be added together and the total voltage thus obtained, is.fed by a separate transmission channel 2 to the control station wheresaid voltage is amplified by the amplifier 3. The amplified voltageserves for modulating inthe modulator 4 an audible carrier .wavesupplied by the local generator 5/ .As disclosed, the audible frequencyof the generator 5 defines the transmission channel considered. 1 17., yI

The modulated Wavepassing 'outof the modulator 4 through the lead 6,reaches a receiver 7 tlieinput into which is also fed through furtherleads 8 with the moducontrol station.

r a s a lated voltages fed by the other channels controlled by-the othergroups of seismographs associated with the same The receiver 7 adds thedifferent voltages supplied by the leads 6 and 8 and feeds them into asingle loud-speaker 9 forming the acoustic indicator.

Furthermore, a number of luminous signalling means are associated witheach lead 6, that is with each group of seismographs. To this end,between the lead 6 and ground, resistances are inserted in series, thenumber of which resistances is equal to the number of luminoussignalling means to be controlled, say four, in the case illustrated inthe figure. 7

These four resistance 10", 1 1, 12 and 13 are mounted in series betweenthe lead 6 and the ground, their values are calculated in a manner suchthat the voltages between their upper ends and ground may formadvantageously a geometrical progression having for 'instance as a ratioe voltage of the connecting point between the resistances 12 and 13 withreference to ground is applied through the voltage limiting system 14 tothe indicator 15, while the voltage of the point connecting theresistances 11 and 12 is fed to the indicator 17 through'the voltagelimiting means 16-, that of the point connecting the resistances 10 and11 to a third indicator 19 through the voltage limiting means 18 andlastly, that of the lead 6 to a fourth indicator 21 through the voltagelimiting means 20. V r

The voltage limiting means 14, 16, 18, 20 are preferably all identical,and are designed so as to limit their output voltage to the maximumvalue which may be usefully applied to the luminous indicators 15, 17,19' and 21 which are also preferably identical with one another.

The operation of the arrangement may be readily explained by assumingthat the indicators become luminous as soon as the voltage applied tothem reaches the value of 1 volt and they supply their maximumluminosity for a voltage equal to /E=3.2 volts or thereabout.

'It is immediately apparent that, by reason by this arrangement, whenthe voltage between the lead 6-. and the ground varies for instancebetween 1 and 3.2 volts or thereabouts, only the indicator 21 subjectedto the voltage of the lead is actuated and passes from its lowercondition corresponding to no emission of light, to its upper conditioncorresponding to maximum luminosity, whereas when the voltage risesabove 3.2 volts, said .indicator 21' remains in its upper maximumluminositycondition, while the indicator 19 begins being illuminated andso on, the indicator 15 showing its maximum illumination only when thevoltage of the lead 6 reaches its maximum.

Preferably, the amplifiers such as 3, are provided with an automaticgain control system, designed so as to give a low gain for signals of aconstant intensity or of an intensity which varies slowly. as in thecase of those produced for instance by a continuous wind, and a largegain for signals having a steep front. Thus a continuous parasiticmovement will produce only a very slight noise in the loud-speaker.

Such automatic gain control means are obviously wellknown in thetechnique of electric communications and geophysical prospection and itis therefore unnecessary to give any example thereof. 7 7

Obviously as many groups of luminous indicators 15 to 21 are used, asthere are groups of seismographs and transmission channels. a

In the case illustrated, the optical signalling means are fed by thevoltage at the output of the modulator 4, but

they may be fed directly by the voltage at the output of the amplifier 3since it is not necessary-for said optical signals to be fed by avoltage which has been subjected to a modification in frequency.

In the case where it is desired to use intermittent sources of lighthaving illuminating frequencies varying as a function of the intensityof the signals, it is sufiicient to insert in series with and beyond thevoltage limiting means 14 to 2.0, generators operating at suitableadjustable frequencies, for instance multi-vibrators incorporatingtransistors or vacuum tubes, the frequencies of such multivibrators orthe like generators being controlled by the voltages at the terminals ofthe resistances 10' to 13.

In the embodiment referred to, the voltages fed by the seisrnographs areapplied individually to the control station where they serve formodulating separate carrier waves.

The amplifiers, modulators and local generators 3, 4 and 5 may be placednext to each group of seismographs and the modulators may feed a singletransmission channel which conveys 'all the informations as a whole tothe control station, said single transmission channel adding thevoltages received and feeding them into the loudspeaker. This cuts. outthus any individual transmission channels, but this advantage is partlyoffset by the fact that it is necessary at the control station toactuate the luminous signalling means through filters so 'as to separateagain the individual channels from one another.

It will be noted that my improved arrangements thus disclosed areindependent of those described in the abovementioned copending priorpatent application and that they may be used simultaneously with thelatter, if required.

The use of luminous signals associated with each channel, allows theoperators 'Whose attention has been drawn by the loudspeaker toascertain immediately which channel or channels has produced the alarmsignal so that they may appreciate upon inspection of the modificationsin the luminosity of the signals, the cause which has sounded the alarmsignal.

Experience. shows, as a matter of fact, that certain causes, such-as agust of Wind progressing along the perimeter of the area to beinvestigated provide an illumination having a characteristic appearance,and for instance they may produce an apparent sliding movement of lightover the board carrying sai d luminous signalling means.

A small amount of experience allows the operators to clearly ascertainthe difference between parasitic and interesting signals.

Many details may obviously be modified in the embodiments describedwithout unduly widening thereby the scope of the present invention, asdefined in the accompanying claims. t

In particular, it is possible to modify the number of optical indicatorscorresponding to each group of seismographs while also said indicatorsmay be distributed in any desired manner on a board, or the like.

What I claim is:

1. An alarm system for a plurality of groups of sensitive geophonesdistributed over a pre-determined ground area for producing signals inaccordance with detected disturbances over said area, said alarm systemcomprising a plurality of amplifying means, each one of said pluralityof amplifying means being connected to a respective one of said groupsof geophones for amplifying signals from each group of geophones, aplurality of audio frequency carrier wave signal generating means, eachhaving a fixed audio frequency carrier wave signal "different from anyother one of said plurality, a plurality of modulator means, each one ofsaid modulator means being connected to a respective one of saidplurality of generating means for modulating the respective audiofrequency carrier wave signal of said generating means in accordancewith modulating signals and each one of said plurality of amplifyingmeans being connected to respective one of said modulator means forproviding amplified geophones signals as modulating signals to saidmodulating means, and a control station including a loudspeaker andmeans to connect all of said modulated audio frequency carrier wavesignals produced by all the modulators to said loudspeaker tosimultaneously energize said loudspeaker.

2. 'An optical system as claimed in claim 1 further comprising opticalalarm means for each group of geophones for receiving amplified signalstherefrom, said optical alarm means for each vgroup of geophonesincluding a" plurality of indicator means each effective for beingilluminated at a particular voltage and means connecting together theplurality of indicator means for each group of geophones to successivelyilluminate the indicator means as a function of theintensity of thereceived ampli- 3'. An alarm system as claimed in claim 1 comprising anoptical alarm system for each group of geophones con- 'nected tothe'modulator means for. the particular group of geophones, each saidoptical alarm system comprising a plurality of series connectedresistances, and optical in- .7

dicators connected successively with said resistors for beingilluminated in succession and with a luminous in- 15 tensity which is afunction of the intensity of the signal received from the modulatormeans.

4. An alarm system as claimed in claim 3 wherein each said optical alarmsystem comprises voltage limiting means for each optical indicatorconnected between the resistances and the respective indicator.

References Cited in the'file of this patent V UNITED STATES PATENTSItaly Mar. 31, 19-36

1. AN ALARM SYSTEM FOR A PLURALITY OF GROUP OF SENITIVE GEOPHONESDISTRIBUTED OVER A PRE-DETERMINED GROUND AREA FOR PRODUCING SIGNALS INACCORDANCE WITH DETECTED DISTURBANCES OVER SAID AREA, ALARM SYSTEMCOMPRISING A PLURALITY OF AMPLIFYING MEANS, EACH ONE OF SAID PLURALITYOF AMPLIFYING MEANS BEING CONNECTED TO A RESPECTIVE ONE OF SAID GROUPSOF GEOPHONES FOR AMPLIFYING SIGNALS FROM EACH GROUP OF GEOPHONES, APLURALITY OF AUDIO FREQUENCY CARRIER WAVE SIGNAL GENERATING MEANS, EACHHAVING A FIXED AUDIO FREQUENCY CARRIER WAVE SIGNAL DIFFERENT FROM ANYOTHER ONE OF SAID PLURALITY, A PLURALITY OF MODULATOR MEANS, ONE OF SAIDMODULATOR MEANS BEING CONNECTED TO A RESPECTIVE ONE OF SAID PLURALITY OFGENERATING MEANS FOR MODULATING THE RESPECTIVE AUDIO FREQUENCY CARRIERWAVE SIGNAL OF SAID GENERATING MEANS IN ACCORDANCE WITH MODULATINGSIGNALS AND EACH ONE OF SAID PLURALITY AMPLIFYING MEANS BEING CONNECTEDTO RESPECTIVE ONE OF SAID MODULATOR MEANS FOR PROVIDING AMPLIFIEDGEOPHONES SIGNALS AS MODULATING SIGNALS TO SAID MODULATING MEANS, AND ACONTROL STATION INCLUDING A LOUDSPEAKER AND MEANS TO CONNECT ALL SAIDMODULATED AUDIO FREQUENCY CARRIER WAVE SIGNAL PRODUCED BY ALL THEMODULATORS TO SAID LOUDSPEAKER TO SIMULTANEOUSLY ENERGIZE SAIDLOUDSPEAKER.